Control for vapor flow valve



June 1, 1965 3,186,641

. W. GOODMAN CONTROL FOR VAPOR FLOW VALVE 4 Sheets-Sheet 1 Filed Jan. 4, 1960 .flll

Invenfor William Goodniav June 1, 1965 w. GOODMAN 3,186,641

CONTROL FOR VAPOR FLOW VALVE Filed Jan. 4, 1960 4 Sheets-Sheet 2 Inventor William. Goodman jH-lprnegs June 1, 1965 w. GOODMAN CONTROL FOR VAPOR FLOW VALVE 4 Sheets-Sheet 3 Filed Jan. 4, 1960 Inventor 'IH-Eorn eys '(Ui'liam Cioodrman'.-

June 1, 1965 w. GOODMAN CONTROL FOR VAPOR FLOW VALVE 4 Sheets-Sheet 4 Filed Jan. 4, 1960 To Powelz LINES To POWER LINES ans:

I'll

Mom .SHAFT Inventor William Goodman B2 ZMaZZaaa.

Morneg United States Patent 3,186,641 CONTROL FOR VAPQR FLOW VALVE William Goodman, 1236 E. Madison Park Ave., Chicago, Ill. Filed Jan. 4, 1960, Ser. No. 363 8 Claims. (Cl. 236-40) This invention relates to a control device for use with a condensing device for condensing vapor and through which the vapor fiows from an inlet to an outlet while being condensed. More specifically this invention relates to an automatic control mechanism including sensing apparatus which is responsive to subcooling of condensed vapor at an outlet of acondensing device and which is adapted to operate a control valve in an inlet of the condensing device.

Such condensing devices may be utilized with various types of vapors, of which mercury vapor and steam are examples, and may also be utilized in various applications. Thus, such a condensing device may be utilized in process work in which material is heated by a steam jacketed kettle and may also be utilized as a radiator in steam heating systems. For the purpose of specifically describing this invention reference will hereinafter be made to a steam system.

In steam heating systems, which employ condensing units such as radiators, it is desired that the steam cover substantially the entire inner surface of the condensing device so that the maximum amount of heat transfer from the condensing device to the ambient air can be obtained. The reason for this is that steam, which has a latent heat ofvaporization of 970 B.t.u. per pound at the standard boiling point, transmits much more heat to the walls of the radiator, and to the ambient air, in the process of condensing to water at a constant temperature than can be obtained by the cooling of water in contact with the same walls since condensate gives up only one B.t.u. per pound for each temperature drop of 1 F. But it is also desirable that the steam within the condensing unit be prevented from flowing from the outlet of the condensing device and entering the outlet conduit. To accomplish this dual purpose, that is, to maintain suflicient steam within the condensing device to obtain substantially complete coverage of the inner walls of the condensing device and yet to prevent the escape of steam into the outlet conduit, it has been common practice to use steam traps at the outlet of the steam using device.

Such traps have employed ball floats, thermostatic elements and other devices responsive to condensate water to open the valve on either a rising water level or a falling condensate temperature and to close the valve on either falling water level or rising temperature. These traps constitute a restriction to the free fiow of condensate from the outlet of the condensing device into an outlet conduit. If the pressure inside the condensing device is modulated by an upstream automatic steam valve, the pressure inside the condensing device may be lower than the pressure in the outlet conduit. When such a condition occurs, 7

the condensate does not drain from the condensing device into the outlet conduit upo'nopening of the steam trap. Instead, vapor or air flows from the outlet conduit through i the trap and back into the condensing device. Such steam traps have also been objectionable by, reason of mechaniawash Fatented June 1, 1965 ture responsive element to control a regulating valve disposed in the inlet conduit for the steam condensing unit. Such a temperature responsive device may be set to maintain a temperature at the condensing unit outlet that is slightly below the temperature at which water can change into steam at a given or desired pressure .within the condensing device. Thus, with the internal steam pressure near the pressure condition at which the temperature responsive element has been designed to operate, such valves restrict the flow of steam to an amount that permits all of the steam to condensate prior to reaching the outlet of the condensing device and provides some subcooling of the condensate below the temperature at which steam and water may exist in a steady state.

While such a temperature responsive control could eliminate many of the difficulties associated with the mechanical-type steam traps, such a control is incapable of maintaining the operation of the steam condensing device at its most eificient point for pressure conditions within the condensing device that vary substantially from the 'desired steam pressure. Because of the operation of an automatic steam control valve, or because of the variations in the pressure of the steam at the-source of supply, the steam pressure within the steam condensing device-can vary over a considerable range. The temperature at which water evaporates into steam or steam condenses into water varies with these changes in steam pressure. As a result, steam pressures within the steam condensing device that are lower than the desired steampressure at which the temperature responsive element is 'set to operate permit an excessive amount of steam to be admitted through the regulating valve so that steam escapes out the open outlet conduit and is wasted and causes difficulties in the'opera-v tion and control of other steam-usingequipment which is connected to the same outlet conduit. sure within the condensing device exceeds the desired pressure at which the temperature responsive element is intended to be operated, the steam admitted to thecondensing device covers only a small portion of the interior surface of the condensing device, and an inefficient operation of the condensing device results.

Steam and water are physically related so that for every steam pressure there is but one single-temperature, called the saturation temperature, at which water can evaporate into steam or steam can condense into water. It is a primary object of this invention to utilize this relationship in a novel manner to maintain substantially the entire inner surface of a steam condensing unit in a steam covered condition and yet prevent excess steam from escaping through the continuously open outlet of the steam condensing device.

It is another object of this invention to control the supply of steam to the inlet of a steam condensing device in such a way as to promote substantially complete coverage of the internal surface of the condensing device with steam. While maintaining at a continuously open outlet of thecondensing device some subcooling'of the condensate below the saturation temperature corresponding to the pressure internal of the condensing device regardless of the internal pressure within the condensing device.

It is another object of this invention to incorporate in an automatic control system for a steam condensing device, a steam regulating valve which is responsive to a pressure internal of the steam condensing device, a predetermined biasing force, and a saturated vapor pressure varying with a fluid temperature at the condensing device outlet in a manner suchthat the valve is positionable by the aforesaid three conditions to maintain subcooling of the condensate at the condensing device outlet for varying internal pressure within the condensing device.

In many instances it is desirable to automatically regulate'the flow of steam to accomplish a dual function. For

If the steam pres= t 3 r example, in steam heating systems or in process work in which material-is heated by a steam jacketed kettle, it is desirable to automatically regulate the steam flow to provide a How that covers a suflicient portion of the interior of thecondensing device with steam to obtain a desired temperature level within the space or the material heated by the steam condensing device and yet prevent theescape of steam out of the outlet conduit. Thermostats sensitive to ambient air temperature or to the temperature of the material have been connected to regulate the supply of steam to steam heating units, but, heretofore, a control system that incorporates a continuously open outlet conduit and satisfactorily regulates the flow of steam to provide both a desired ambient air temperature or masponsive to an ambient temperature and to subcooling.

of condensate at an outlet of the condensing device to pre vent the escape of steam outthe'outlet of the'condensing device while maintaining the interior of the condensing device in a steam covered condition.

Yet another object of this invention is to incorporate in an automatic control system for a steam condensing device a pneumatically actuated valve for regulating the flow of steam to the condensing unit and to position the steam regulating valve by regulating the actuating air pressure supplied to the valve under the joint control or a thermostat responsive to an ambient temperature and a steamlimiting relay responsive to a fluid temperature and to the pressure at the condensing unit outlet in order to maintain a selected ambient temperature and maintain a sub-cooled condition of the condensate at the outlet of thecondensing device. a 7

Still another object of this invention is to incorporate, in

an automatic control system for a steam condensing uni-t, an electric control circuit for positioning a steam-regulatin valve and to include in the control circuit apparatus varied in response to an ambient temperature and addrtional apparatus varied in response to a steam-limiter unit that senses a fluid temperature and a pressure at the condensing unit outlet whereby the valve is normally positionable by the ambient temperature responsive apparatus to maintain ade'sired'ambient temperature and the steam limiter responsive apparatus is operative to override the.

ambient temperature responsive apparatus on low ambient temperatures to maintain a'sub-cooled condition at the outlet of the condenser outlet.

Other and further objects of the present inventiomwill be apparent from the following description'and claims and are illustrated in the. accompanying drawings, which, by way of illustration, show preferred embodiments of. the

present invention and the principles thereof and what I FIG. 2 is a plan view of a control valve assembly shown in side elevation in FIG. 1; v

, FIG. 3 is an elevation view, partly in section, of an-. other embodiment of a control valve assembly;

FIG; 4'is an elevation, partly in section, of a control valve assembly which incorporates the partial pressure of I a fluid as a biasing force; FIG 5 is an elevation, partly in section, of another: embodiment of a control valve assembly;

FIG. 6 is a schematic view invention which incorporates a control valve; 7

FIG. 7 is an enlarged detailed view, in section, of a steam-limiter assembly-whichcan be utilized in the embodiment illustrated in FIG. 6; j

FIG. 7A is an enlarged detailed view, in section, showing a steam-limiter assembly as illustrated in FIG. 7, but mounted remote from a condensing device ;.and

FIG. .8 is a schematic View of an electrical control system torregulating the supply of steam to a steam condensing unit. I e

As described hereinabove steam and water are physically related so that for every steam pressure there is buttone single temperature,: called the saturation temperature, at which water can evaporate into steam or steam can condense into water. This. invention utilizes that relationship to maintain substantially the entire inner surface of a steam condensing unit in asteam covered condition while preventing excess steam from escaping out the continuously open ,outletoi' the steam condensing device. The mannerin which this is accomplished will be explained more fullythereinbelow in relation to the embodiment illustrated in FIG; 1.

In FIG-,1, there is illustrated a stea nrcondensing device 11, shown, as a steam kettle. Aninlet conduit 12 is connected to the jacket of the steam'kettle to supply steam to the jacket from a suitable source (not illustrated). .An outlet conduit 13 is connected to an outlet 14 on the steanrkettle for conveying condensate to an outlet conduit. The'direction'of the flow of steam through the conduits 12 and 13 is as indicated by the arrows'shown in FIG. 1. In the inletconduit 12 there is. an enlarged body 15 which contains an internal'dividing wall 16; A valvelii is provided by avalve seat 17 formed in the wall 16 and a valve element 18, movable in a vertical direction, as viewed: in FIG. 1, with respect to the valve seatl'? to vary the area of the oriflee-afforded between 'the'seat 17 and the valve element 18. An elongated rod 19 is attached to the valve element 1S and extends through an. opening 21 in the body 15. A housing 22 is supported in fixed relation on the of an embodimentof the pneumatically actuated body '15 by vertically extending brackets 23. The hous ing 22 comprises disk-shaped upper and lower portions respectively designated 24iand 2S and which have outwardly directed flanges 24F and-25F. A flexible diaphragm or bellows 26' is clamped between the flanges 24F and 25F and the flanges are secured "together in a fluid-tight scaling relation as by bolts 29. The flanges may be welded or brazedrather thanbolted as illustrated. The rod 19 extends through an opening 31 in the lower housing'portion 25 and is attached at its upper end to a plate 3Z,'which,' in turn, is secured co the'fiexible diaphragm 2s. Thus,,any movement of the diaphragm 26 causescorresponding movement of'the valve element 18. As will be explained hereinafter; the diaphragm .26 acts as sensing means responsive to subcooling of condensate at the outletxand efliectiveto hold the- Valve 2t) open so long as more than a selected minimum subcooled condition of the diaphragm. V V I a A flexible bellows-type seal 33' is attached at one end to the rod 19 and at its opposite end-to the upper face of the body 15 to surround the outer periphery of the opening 21 and thus prevent escape of steam while permitting free vertical'movtement of the rod,v In like manner a flexible bellows-type seal 34, also aflix'ed to the rod 19, provides a fluid-tight seal for the opening 31-; Various types of sealing means may be utilizedfor providing condensate is sensed I by the i fitting 41 is threaded in the outlet opening 14. A thinwalled, elongated bulb 42 is threaded within the fitting 41 and projects through the outlet opening 14. A capil lary tube '43 is connected at one end to the bulb 42 and at its other end projects through the upper housing portion 24 at connection 40 'so as to be in communication with the chamber 27. The fitting 41 has a port 44 formed therein. A pressure transmitting tube 45 is fitted within the opening 44 at one end and at its opposite end is fitted within an opening in the lower housing portion 25 so as to transmit the pressure at the outlet of the steam condensing device with the chamber 28.

The bulb 42 is partially filled with a volatile liquid, such as water. Since the walls of the bulb 42, the capillary tube 43, the diaphragm 26, and the upper housing portion 24 present a closed container, hereinafter referred "to as the power unit, a saturated vapor condition is obtained within this closed container. The vapor pressure resulting from this saturated vapor condition is a function of the ambient fluid temperature at the bulb 42 and the resulting pressure acting on the upper surface of the diaphragm 26 exerts a downward force on the rod 19 to move the valve element 18 in a closing direction. The pressure at the outlet end of the condensing unit 11, transmitted through the conduit 45 to the chamber 28, exerts a force on the under side of the diaphragm'26 tending to move the valve 19. and valve element 18 upwardly in an opening direction.

The operation of the embodiment of this invention shown in FIG. 1, and the manner in which substantially complete coverage of the interior walls of the steam con-- densing device by steam is maintained while permitting only condensate to-flow out the outlet conduit will now be described.

Toinitiate operation, steam is supplied through the conduit 12 and through the valve 20, which is maintained 'in an open condition by the pressure within the chamber 28, and into the jacket of the steam condensing unit, shown as a steam kettle 11. The steam in contacting the walls of the kettle gives up heat to the walls of the kettle,

, condenses into its liquid state, and flows out the conduit the valve 20 to the steam kettle 11 to just that amount which will cover substantially all of the interior surface of the steam kettle but yet permit a small portion of the interior surface area near the outlet of the condensing unit to cool the leaving condensate below the saturation temperature in the area immediately adjacent the outlet 14, no steam escapes out the conduit 13. On the other hand, if the condensate is at the saturation temperature, steam could be, and most probably is, leaving the steam kettle.

As noted above, the liquid within the bulb 42 and the confined volume obtained by the sealed character of the chamber 27, the tube 43, and the bulb 42 permit a saturated vapor pressure to be obtained within the chamber 27, which is a function of the temperature of the ambient fluid at the'outlet 14. As the ambient temperature increases, the pressure in the chamber 27 increases. Likewise, as the' ambient temperature decreases, the pressure in the chamber 27 decreases. As viewed in FIG. 1 the resultant force, acting downwardly on the rod 19-toclose the valve 20, is opposed by a force which is a function of the pressure at the outlet 14 as transmitted to the chamber 28 by the conduit 45. Thus, the force due to the pressure of the fluid atthe outlet 14 acts in opposition to the force due to the temperature and, in effect,

acts to reference theactual temperature at the outlet to the saturation temperature at that particularpressure.

fltemperature'corresponding to the actual steam pressure within the condenser, as transmitted to the chamber 28. The magnitude of this temperature differential, or subcooling of the condensate, is determined by the bias afforded by the spring 37.

As an example, at 20.8 pounds per square inch absolute pressure the boiling point of water is 230 F. If the condensate water at the outlet 14 is less than 230 F. and the pressure is 20.8 pounds per square inch absolute, no steam is present at the outlet 14. A temperature of 230 F. causes a corresponding pressure to be developed within the chamber 27. In such an instance the biasing spring 37 and the force dueto the pressure within chamber 27 overcomes the force due to the 20.8 pounds per square inch pressure in the chamber 28 and the valve 20 is moved toward a'clos'ed position to restrict the flow of steam to portion of the wall will be covered with condensed water. a

' 'If a sufficiently large flow-of steam were permitted to flow through the valve 20, it is obvious that ultimately. live steam, rather than just condensate, would be exhausted through the conduit 13. However, before this condition occurs, the automatic control elements of this invention are cooperative to regulate the flow of the steam.

As mentioned hereinabove, for every steam pressure, there is but one single temperature at which water can evaporate into steam or at which steam can condense into water. As a result water can be subcooled below the saturation temperature corresponding to the pressure only if there is no steam present above the water. Thus, it

the steam condensing device 11 since such a temperature at such a pressure indicates that live steam is exhausting out the conduit 11, and is thus being wasted. If the condensate should become subcooled so that the desired amount of subcooling is exceeded for the 20.8 pounds per square inch absolute internal pressure, as for example say a temperature below 215 F., the pressure in chamber 28 moves the valve 20 to admit more steam to raise the condensate temperature back to 215 F.

Thus, the biasing force of the spring 37 requires that the force due to the saturated vapor pressure within the temperature responsive bulb 42 be of a lesser magnitude than the internal pressure of the steam within the steam kettle as transmitted to the chamber 28. This biasing force may be adjusted by varying the compressive force of the spring 37 to provide any desired degree of subcooling. The force of the spring 37 is preferably adjusted to be of a small magnitude so that the temperature of the condensate is only slightly lower than the saturation tem- I perature so'that the jacket of the steam kettle is substantially completely filled with steam and thus operates at a high efiiciency.

In the foregoing manner the valve admits only as much steam as can be condensed No steam can flow into the return line, but condensate can drain freely from the steam unit into the return line. This mode of operation is based on a differential between the pressure within the conaisasar ures within the condensing device to maintain operation of'the condensing device near its maximum efiiciency by maintaining substantially the entire inner surface in a steam covered condition, and yet prevents any waste of steam through the conduit 13. By reason of the force balanced relation of these pressures, the supply of steam to the steam kettle is regulated independently of any variations in the-pressure of the steam at the source'ot supply.

The control assembly illustrated in FIG. 3 is somewhat similar to that illustrated in FIG. 1 and like reference numerals are used to indicate like parts except that the suffix A has been added. In FIG. 3 thebodyldA has a port 51 formedin an upper wall. The lower housing portionZSA has a port 52 formed therein and a pressure.

vices substantially the same as the pressure at the outlet otthe steam condensing device 11. Thus, a relatively short conduit 53 can be utilized for transmitting the steam pressure to the underside of the diaphragm 26A in place ofthe conduit 45 as illustrated in FIG. 1; :The pressure line 53 of the PEG. 3'embodirnent. illustrated in FIG. 3

4" 3 packing s2 is disposed within the flange er andprovi-des a fiu-id-tight seal along the .inner periphery of the flange and the circumferential surfacev of the rod 193 so that the pressure within the chamberldB is the same as that with in'the' condensing device 11. A packing gland .63 is threaded within the flange 61 to compress the packing to force.

provides a more direct connection, but the operation of the control valve assembly is the same as that set out above in detail in relation to the embodiment shown in FIG.

In the embodiments shown in F165. 1 to 3, which utilize'a mechanical compression spring for the, biasing f force-the temperature sensing bulb 4-2 is preferably an evacuated bulb to which the small amount of, liquid necessary for obtaining the temperature indicating saturated vapor condition has been added. 'Biasing arrange:

ments other than a mechanical compression spring may illustrated in' FlG. 1 are indicate-d .bylike reference nu merals but with the addition of the suffix fB. With this arrangementthe temperature of the condensate'sun' rounding the 'buIb' lZB causes a saturated vapor pressure to be developed within a chamber 27:? and this saturated vapor pressure is the same function of the condensate pressures in these chambers are equal.

a tight,*sealing relation withvthe rod 193 and the inner periphery of the flange 61 and also to retain the packing within the flange. 1

At the other end of the rod 1 23 a similar packing gland seal is provided. Thus, as viewed in FIG. 4, theenlarged body 15B is provided with an upwardly directed flange 64. A washer 65 resides on a base face 56 of a counterbore formed above the opening-21B; This washer provides a back-up surface for the packing 67; and a packing gland 68, threaded within the flange 64, compresses the packing 67' against the-washer 6-5to, force the packing into fluid-tight sealing relation with the internal periphery of the flange 64 and the external circumferential surface of the rod 19B.

- For the purpose of establishing the biasing force which isdeveloped by the partial pressure of the air or other gas withinthe power unit, the upperhousing section 24B is formed with an upwardlydirected flange '71; A short tube '72 is secured within the flange 7 1 through which air or other gas is admitted to establish the desired biasing Thereafter the free end of the'tube is sealed so that the charge willbe, maintained in the thus seal-ed power unit.

In operation of the embodiment illustrated in FIG. 4,

thesaturation vapor pressure which is a function of the temperature of. the condensate at the condensing unit outlet as sensed; by the bulb 42B and the partial pressure of the .unevacuated air withinthe chamber 273 exerts t-herod 193 through the diaphragm 26B to move the valve 23B toincrease thesize of the passage for steam flowthrough thevalve. Because the'pressur-es in chamhere 275 and 2 83 act oppositely on the diaphnagm 26B the valve 2633. is in "a positoin of equilibrium when the in the chamber 278 is the sum of the saturatedvapor pressure ofthe bulb QZBandthe partial pressureot the air. orother gas. Therefore, the saturatedvapor pressure must be less than that of the steam. within the steam unit.

This relation'ship of forces positions the valve ZtiB to regulate the flow of steam to'that amount'that will provide temperature as was the pressure developed in the charm ber 27 in the embodiment shown in FIG. 1. pressure,'developedrwithin the chamber 273 is equal to the sum of the: saturated vapor pressure and't'he. partial pressure due to the air or other gas. The partial. pressure of the ai-r'or. othergas thus develops'a fixedbiasing force which is transmitted to the. rod .IJB through theflexible diaphragm ZEBL'and this fixed biasing force determines the degree of subcooling of the condensate at the con- The total densing device outlet that willbe automatically "main tai'ned. In this manner the action of the partial pressure of the unevacuated air within the power unit affords a biasing force like the. force of the compression'ispring .37 of .the

example, a flexible bellows, or a flexible diaphragm or a V suitable packing gland may be used. In the embodiment illustrated in FIG. 4'. packing glands aroused.

Inthe embodiment shown in FIG; 4 thelower housing portion 25 is formed'with a downwardly d rected flange 61 which surrounds the opening 31.: Annular-shaped.

at the outlet sorn'esubcooling of the condensate water below the saturation -temperature corresponding to' the steampressure within the steam unit. The condensate is V 7 thus required tol'be subcooled below the saturation terng perature corresponding to .the'steam pressure within the amount, of subcoo-ling is determined bythe biasing: force provided by the partial pressure of'theair or. othergas within the power unit. j

.. FIG.:5 illustrates another embodiment of the invention wherein a regulated air .pres-sure'issuppl ed to the In the embodiment illustrated in FIG. 5 an upper.

housing assembly 8 1 co-mprisesan upper. housing portlon 244C and a lower housing portion 83. The entire housing is supported by bracketsZSC from. anenlarged 1 body 150. A capillary ,tu-bedFaC is connectedwith the upper housing section 2 4C in a standard flangedcoupling 4t-Cso that a saturated vapor pressure, which is V a function of the condensate temperature at the =condens= The pressure a I fluid and the conduit 95 is connected to exhaust.

. s. ing device outlet, is supplied to the chamber -27C as in the embodiment illustrated inF-IG. 1. A conduit 45C is disposed in a fluid-tight sealing relation within A bellows 80 provides a seal about 'the upper portion of the rod'19C.

A' packing gland sealing assembly comprising an upwardly directed flange 640, a back-up washer'65C, a packing 67C,-and'a packing gland 68C, provides a seal around the valve end of the rod 19C as described with reference to the corresponding assembly in FIG. 4.

The lower housing portion 83 is constructed to have a greater thickness in section as compared to the lower housing section 25 of the FIG. 1 embodiment illustrated in FIG. 1. A conduit 84 having openings 85 and 86 in the lower face of the section is formed within this enlarged portion. A flexible bellows 87 is attached to one end of the lower face of the housing sections?) and is attached at the opposite end to a disk788. The disk 88 is rigidly connected to the rod 19C. An airline 92 has one end disposed within the opening 85 in a flanged coupling 93. The airline 92 is divided into apair of branch conduits 94 and 95. A valve 96 has elements 97' and 98 disposed in the branch conduits 94 and 95 respectively. The conduit 94 is connected to a source of high pressure air or other The elements 97 and 98 are so dimensioned that'rnovement of the valve in one direction, downwardly as illustrated in FIG. admits high pressure fluid to conduit 921mm conduit 94 While restricting any fiow tno m'conduit 92 to conduit 95. Movement of the valve 96 in an opposite direction permits flow of fluid from conduit92. to exhaust through conduit 95 while restricting any -fiowfrom the conduit 94 .to the conduit 92. Thus, the pressure within *the bellows 87 may be regulated to be any portion of that ally or automatically controlled.

Other means, such as a conventional adjustable valve and restricted bleed arrangement, can be used to regulate the pressure within the bellows 87. I

.In operation, the pressure within the bellows 87 provides a biasing force which is similar to that obtained by the spring 37 in the embodiment illustrated in FIG. 1. This biasing force, acting in conjunction with the opposed temperature generated pressure and steam pressure forces on diaphragm 26, positions valve 20 to maintain subcooling of the condensate below the 'saturation'tem peratu're corresponding to the pressure withinl the steam condensing device in the same manner as described'in the operation 'of the embodiments illustrated in FIGS. 1-4.

In all of the embodiments illustrated in FIGS. 1-5 the valve element 13 is illustrated as being moved downward- 1y with respect to the valve seat' 17 to close the valve. A reverse acting valve can be utilized :by reversing the connections of the pressure andbiasing forces to the rod 19.

The automatic steam regulating control described hereina'bove can be used not only alone, as asepara'te and independent control, but it also can be u'sedin conjunc:

a multi-coil radiator 101. A steam supply conduit 162 is connected tothe inlet 103 of the radiator 161 andhas an enlarged body lMdisposedwithin the conduit. Avalve 105 is disposed within the body 164 and regulates the amount oi? steam flowing through the conduit 102. A

housing 106 comprising an upper portion 107 and a lower portion 108 having a flexible diaphragm 1199 clamped between the portions 107 and 108 to divide the interior of the housing into an upper chamber 111 and lower chamber 112. A bellows or a piston could be substituted for the diaphragm 109. A rod 113 is connected at opposite ends to the diaphragm 169 and the movable element of the valve positions the valve in accordance with the movement of the diaphragm. A spring 114 is connected to bias the valve 105 in an opening direction. A conduit 115 is connected to a source of supply of high pressure air at one end and is connected at its opposite end to the housing portion 107 to supply the high pressure air to the chamber 111. A restricted bleed, not illustrated, may be incorporated in the thermostatic valve 118 or the conduit 115. The conduit 115 is provided with .a pair of parallel branch conduits 116 and 117. A thermostatic valve 118 is disposed in the conduit 116. This thermostatic valve is responsive to ambient air temperature or to some other ambient fluid temperature in the case of other steam heating devices. The thermostatic valve 118 is normally closed and is opened upon the ambient air temperature exceeding :a predetermined magnitude. The branch conduit 117 has a valve unit 119 disposed therein. This unit is shown in detail in FIG. 7.

Referring to FIG. 7, the conduit 117 has an enlarged fitting 121 disposed therein. An inner web 122 extends across the interior of the fitting 121 and has'a valve seat 123 formed therein. A valve element 124 is movable toward and away from the valve seat 122 and 123 to enlarge or restrict the valve orifice 125. A rod 126 is connected to the valve element 124 to produce this movement. A pair of brackets 127 support a housing 1281mm the enlarged'fitting 121. The housing 123 has a threaded nipple 129 projected from one face. The nipple 129 is threadedly engaged within a fitting 131 formed with the outlet conduit 110, see FIG. 6. An interior web 132 extends across the interior ofthe housing 128 and is provided with orifices 133. A flexible bellows 134 is attached at one end to the web 132 and is attached at the opposite end to a disk 135, which, in turn, is rigidly connected to the rod 126. A diaphragm could be substituted for the bellows 134. A bulb 136 extends through an opening 137 in the disk 13-2 to provide communication between the interior of the bulb and the interior of the bellows 134. The bulb. is partially filled with a volatile liquid. The bellows and bulb assembly provide a confined volume so that the temperature surrounding the bulb 136 causes a saturated vapor pressure, which is a function of the temperature surrounding the bulb, to be developed within the bellows 134. I A packing gland assembly comprising a flanged portion 137, a packing 138, and a packing gland 139 provides a sealar-ound the rod 126 at the point at which the rod enters the housing. A bellows seal 141 is provided to prevent leakage of the high pressure air from the point at which the rod 126 enters the housing 121. A disk 142 is threaded on the rod 126 and locked in position by a lock nut 143 at a point intermediate the fitting 121 and the housing 128. A coiled compression spring 143 acts against thedisk 142 and the housing 128 to bias the valve toward an open position. 7 I

In operation, the steam regulating valve is normally positioned in response to the' action of the thermostatic valve 118. The thermostatic valve 118 permits a sufiicient flow of air to pass through the conduit 116 and the conduit 115 to the chamber 111'to force the diaphragm 109 downwardly. The thermostatic valve 118 is positioned by temperatures lower than the predetermined maximum temperature to restrict the flow of air through the conduits 115 and 116 to the chamber 111 so that the force developed on the diaphragm 189 is somewhat less than the biasing force of the spring 114. The biasing force of the spring therefore moves the valve 165 toward an ope-n position until the force of the spring equals that of the air pressure in the chamberlll. This permits steam to flow to the radiator 1M. If the flow of steam thus obtained causes the radiator to raise the valve 113 opens widerto permit more air to flow to the assembly 119 and housing 128 be mounted'immediately' adjacent the condensing device, and in FIG. 7A there is illustrated an'arrangement wherein such components are located at aposition remote from the condensingrdevice. In FIG. 7A parts which correspond to like parts in FIG.

7 are indicated by like reference numerals but with the 1 addition of a prime mark In the arrangement illustrated in PEG. 7A a conduit 301 conducts'the pressure at the outlet. of the condensing device to the interior of. the housing 128', and a conduit 332 is utilized'to connect the interior of the bulb 136' with the interior of the bellows 13d. The operation of the arrangement illustrated in PEG; 7A is like that'of the arrangement illustrated in FIG. 7 and described hereinabove.

It is possible, witha low ambient 'air temperature at the thermostatic valve, for the thermostatic valve to position the steamvregulating valve 1&5 so that a greater amount of steam fiows to the radiator than can be condensed withinthe radiator. Under such circumstances the steam would flow out the outlet conduit 1169' and would 1 therefore be wasted. Also itwould cause difiiculties with other steam condensin'gdevices connected to' the same outlet conduit 1%. The valve assembly 119 acts as a steam limiter under such circumstances to prevent such an excess flow of steam; a

The bulb 136, which is disposed within the outlet 110 of the radiator, senses the temperature of the fluid sur-.

rounding the bulb and a saturated vapor pressure, which is'a function of this fluid temperature, is generatedwithin the bellows 134. This pressure acts on the rod 126 to move the valve 125 in an opening direction. The pressure within the radiator is transmitted through the hollow nipple 129 to the interior of the housing 128. The apertures 133 permit the pressure to act on the exterior of the bellows 134m develop a force which acts in opposition to the force developed by the temperature responsive pressure within the bellows. Thus, the pressure within the radiator acting on the bellows 134 causes the rod 126 to move in a direction to close the valve 125. The spring 143 exerts a biasing force onthe rod 126 which tends to move the valve 125 in the same, opening direction as the saturated vapor pressure within :the bellows 134, Instead of thexspring 143, air could be used as the biasing force with constructions similar to F163. 4 and ,5. Since the saturated vapor pressure and'the. pressure interior of the radiator act on equal areas, the temperature of the condensate leaving the radiator must be less than the saturation temperature corresponding .to the.

restrictthefiow of steam through the valve to just that amount that will cover. substantially the entire inner surface of the radiator and still provide subcooling, asdetermined by the setting of the spring 143, at the outlet of the radiator. r V

Steam regulating valves are sometimes employed that act oppositely that shown by the valve assembly 1&6 in

' PEG. 6. That is,it is possible for a valve'such as lltld to be biased toward a closed position rather than an open position as illustrated. Thus, the valve element 125 carriedby the rod 113 could be disposedbelow the valve seat formed in, the housing 1ti4,'as viewed in FIG. 6, and the air pressure in chamberlillwould be effective to open the valve E535. Appropriate'changes in the thermostat and steam-limiter wouldalso be required.

Also, and as pointed out hereinabove with reference to FIG. 7A, it is not necessary that the steam limiter be mounted directly adjacent the outlet of the steam [corn densing device. Instead, in some. instances it may be desirable to locate the steam limiter at a position remote from the condensing device, as by utilizing conduits 581 and 302 as illustrated in FIGi 7A. Y

The steam limiting control described in'the preceding embodiments of this invention can be readily incorporated in an electrical. control systemto provide control of a steam supply either independently of or in conjunction with other control devices. Different electrical circuits can be used FIG. 8 illustrates one embodiment of the invention wherein the steam regulating control assembly is incoporatedin an electrical control system to regulate the supply of steam to a condensing device in conjunction with a roomair thermostat.

In FIG. 8a motor shaft 171 is connected to a steam V C1 and C2 areselectively energized "to cause rotation of the-motor, indicated diagramatically. at. M, and the motor shaft 171. Energization or" coil C1 energizes the 'motor to rotate the shaft 171 in aclockwise, closing direction. Energization ofcoil C2 causes the motor to rotate the shaft 171 ina counterclockwise direction ,to'further pressure within the radiator to maintain the valve 125 in a closed position. If the, temperature of the condensate approaches the saturation temperature corresponding to the pressure within theradiator, the saturated vapor pressure within the bellows'llfed approaches therpressure' 117 and 115 therefore results, and the resulting buildup in the chamber 111 forces the valveldS toward a closed position to restrict the flow of steam into the radiator.

Thus, even-thoughthe thermostatic valve 118 may be callingfor a wide open position of the steam regulating valve 1&5, the steam limiting relay .119 is operative to open the stream-regulating valve.

- The power for energizing the coils'Cl and C2 is obtained from the outputtta'ps T1 and T2 of a transformer T which is connected to a power line as indicated by the legend., The coils C1 and C2 are connected together at 173 and a line 174,; shown in dashed outline, connects the coils to the tap TL A balancing relay 175 is connected to the tap T2 of'the transformer byrneans of line 176. As viewed in FIG'. 8 the balancing relay T is pivoted about point 1751 and includes. a downwardly dependingarm 177 which'has a contact 178 at its outermost. extremity. The balancing relay includes a 'yoke 179 which has a pair of upwardly projecting arms. 181 and 182 which are'disposedwithin coilslSS and 184 respectively. 7

A pair of contacts-185 and-i186 are'connected-to the coils C2 .andCl' respectively at the ends opposite connection 173. The contacts 185 and 18s) are spaced from the contact 178 of 'thebalancing relay 175 so that, in a balanced condition of the relay as illustrated, neither contact 185 nor 186 is engagedwith'the contact51l78. In this condition neither coil Cl nor coil C2 is energized 183 and 184 areequallyenergiz'ed. Upon one coil becoming energized. to a greater.. extent than the other coil, the yoke 179 is caused to rotate about the pivot 175? to move thecontact 173 into contacting relation 3,1 13 'with one of the contacts 186 and 185. Under such circumstances one of the coils C1 and C2 is energized by the flow of current through the lines 174 and 176 and the motor shaft 178 moves the steam-regulating valve in a closing or openingdi'rection, as the case may be. Aline 187 is connected at one end to the tap T1 of the transformer and is connected at its other end to a'mova- "blea'rm-188 of a potentiometer 189. A line 191 is connected at one end to-the tap T2 of the transformer and is connected at its opposite end to a movable arm 192 or a potentiometer 193. The potentiometer 189 includes a resistance'194 having ends 195 and 196. The potentiometer 193 includes a resistance 197 having-ends 198 and 199. Ends 195 and 198 of potentiometers 189 and 193 respectively are connected to opposite ends of the coil 184. End 199 of the potentiometer 193 is connected to one end of mean 183. A line 201 connects the opposite end of the 'coilto the end 196 of the potentiometer '189.

A potentiometer 202 is disposed in the line 201. The potentiometer 202 includes a resistance 203 and a movable arm 204. A steam-limiter control 205 is connected through the linkage 206 to the movable arm 204. The steam-limiter assembly 205 is basically that shown in detail-in the embodiment illustrated in FIG. 7 and like reference numerals,'but with the addition of the suflix fiF, indicating like parts. The assembly 205 comprises ahousing 128F' and a flexible bellows 134E disposed within the housing, a temperature sensing bulb 136]? for generating a saturated vapor pressure in the interior of the bellows 134F, a conduit 131F for transmitting a pressure internal of a steam condensing unit to the interior of housing 128F and a spring 143F for biasing link 206 in the same direction-as the saturated vapor pressure within'the bellows 134F.

. A temperature responsive element 208 is connected to the movable arm 188 of the potentiometer 189 through the link 209 to alford a thermostat The movable arm 192 of the potentiometer 193 is connected for movement by the motor shaft 171 by means of linkage 21 1.

. It can be seen that the line 187 is connected to the line 191 by means of two parallel circuits. .As viewed in 'FIG. 8, the portion of the resistance 194 to the left of constitute one branch of this parallel circuit. The por-' tion 194 of the resistance to the right of the sliding contact'1 88, the portion of the resistance 202 to the'l'eft of contact-204, the coil-183, and the portion of the resistance 197 to the right of the sliding contact 192 constitute the other branch of this parallel circuit. Any movement of the sliding contacts 188, 204, 192,

. acts to vary the relative resistances of the parallel branches and results in unequal current flow through the two parallel circuits and unequal energizati-on of the coils 183 and '184. As viewed in FIG. 8, leftward movement of the slid- .ing contact 188 on the resistance 194 subtracts resistance from the branch which contains coil 184 and adds re- .the sliding contact 188, the coil 184, and the portion of V the-resistance 197 to the left of the sliding contact 192 and 186 so that coil C1 is energized to cause clockwise rotation of the'shaft 171 to close the steam-regulating valve. Inlike manner, low ambient air temperature at the thermosttf208 results in'the energizing of the coil 183 to energ'ize coil C2 and open the steam-regulating valve. Any

14 Thus, the steam-regulating valve is moved to a new position by a temperature variation at the thermostat and is maintained in that new position by the rebalancing of the electrical network through the'potentiometer 193.

With sufficiently low ambient air temperature at the thermostat 208 it is possible for the steam-regulating valve to be positioned to supply a greater amount of steam to the steam condensing unit than can be condensed within the unit. Under such circumstances excess steam would be exhausted out the outlet. The steam-regulating unit 205 and the potentiometer 282 prevent such a condition from occurring. When the temperature of the condensate at the condensing unit outlet approaches the saturation temperature corresponding to the pressure within the "condensing unit, the saturated vapor pressure within the bellows 134F and the biasing spring 143F are operative to move the link 286 rightwardly against the force due to the internal pressure within the condenser as transmitted to the interior of the housing 128R This rightward movement of the link 2% moves the slidable arm 204 along the resistance 283 to add resistance to the branch which contains the coil 183. Thus the energization of the coil 183 with respect to the energization of the coil 184 is reduced and the yoke 179 is rotated in a clockwise direction about the pivot point to engage the contacts 178 and 186. Engagement of these contacts energizes the coil C1 to rotate the motor shaft 171 in a clockwise and steam-regulating valve clos 'ing direction as viewed in FIG. 8. Thus, the steam-limit ing control assembly 285 acts on the thermostat control when the thermostatic control calls for such a position of the steam-regulating valve as results in too little subcooling of the condensate leaving the outlet.

As in the other embodiments of the invention, the manner in which the pressure internal of: the steam condens-' ing unit is combined with the temperature responsive force and the biasing force results in a position of the steamregulating valve that supplies that amount of steam to the steam condensing device that covers substanially the entire inner surface of the condensing device and yet maintainls su-bcooling of the condensate at the condensing device out et. 4

Hence, while I have illustrated and described the preferred embodiments of my invention, it is to be understood that these are capable of variation and modification, and I therefore do not Wish to be limited to the precise details set forth, but desire to avail myself of such changes and alterations as fall within the purview of the following claims.

I claim:

vapor condensing device has an inlet conduit connected to a source of supply of vapor and a continuously open outlet connected to an outlet conduit, a control mechanism for regulating the supply of vapor to the condensing device comprising, a regulating valve disposed in the conduit for governing the amount of vapor suppliedto the condensing device, first means responsive to the fluid temperature at the outlet of the condensing device for moving the valve in a closing direction, second means responsive to the fluid pressure within the condensing device for moving the valve in an opening direction, a flexible element connected to the .valve to exert a biasing force to move the valve in a closing direction, and conduit means connected to'supply a fiuid under pressure to the ilexibleelement, whereby the pressure acting on the flexible element maintains a differential between the temperature of the fluid at the condensing device outlet and the saturation temperature corresponding to the pressure internal of the con-. densing device soas to maintain a sub-cooled condition of the condensate at the outlet as determined by the biasing means for any vapor pressure within the condensing device.

2. For use with a vapor condensing system of the kind having a vapor condensing device, an inlet conduit interconnecting the inlet of the condensing device with a source of vapor and an outlet conduit connected to a continuouslyopen outlet of the condensing device; control mechanism for regulating the supply of vapor to the condensing device comprising, a regulating valve disposed in the inlet conduit, electric power means connected to the valve to 7 move the valve in opening and closing directions, a con trol member movable to actuate the power means to move the valve in said two'd-irections, a housing having a pressure responsive element connected to the control member, temperature sensing means responsive to the fluid temperature at the outlet of the condensing device connected to the housing tomove the pressure responsive elementand the control memberin a first direction, a conduit having an open end in communication with the interior of the con denser and connected to the housing to move the pressure responsive element and the control member in a second direction opposite to the first direction, and biasing means connectedrto move the control mem berin the first direction, whereby the regulating valve is positioned by the action of the control member to maintain subcooling of the fluid at the condensing device outlet.

3. For use with a vapor condensing system *of the kind 1 having a vapor condensing device, an inlet conduit interconnecting the inlet of the condensingdevice with alsource of vapor and an outlet conduit "connected to a continuously open outlet of the condensing device; control mechanism for regulating the supply of vapor to said condenser comprising, a regulating valve disposed in the inlet conduit; electric power means'connected to the valve to move the valve in opening and closing directions, a first conQ trol member movable to actuate the pov er means to move 7 the valve in said two directions, a housing having'a presmember, temperature at the outlet of the condensing device connected to the housing to move the pressure responsive element and the control member in a first direction, a conduit having an open'end in communication with the interior of the condensing device and connected to thehousi 'ing to move the pressure responsiveelement and the first control member in asecond direction opposite to the first direction, biasing means connected to move the first con trol ,rnember in thefirst direction, the regulating valve being positioned by the action of the first control memensaeei i i element and the first potentiometer: in a second direction to cause closing movement of the valve, the; regulating valve being positioned by the first variable potentiomete to maintain .subcooling' of the fluid at the condensing device outlet, and a thermostatyresponsive to. temperature to'be affected by the condcnsing deviceand connected to .the second variable potentio'meter fo-r moving theregulating valve towarda closed'position when the affected temperature exceeds a predeterminedmagnitude.

5. A control device effective to regulate the flow of vapor from a source thereof to a condensing device having an outlet and in which device the vapor is'condensed and subcooled below the condensing temperature comin a direction opposite to said first direction whereby said.

sensing means so controls operation of said regulating means as to maintain a subcooled condit on of the condensate at the outlet as determined by said biasing means.

6. For usewitha vapor condensing system of the kind.

having a vapor condensing device, an inlet conduit interconnecting the inlet of the condensing device with a source of vapor and an outlet conduit connected to a continuously open outlet of the condensing -;device;' a control mechanisrnior regulating thesupply of vaporto the condensing device comprising a'pneumatically actuated valve for controlling the supply of vapor to the condensing device, pressureresponsive' means for'actuating: the valve in closing and opening directions, an air regulating valve for regulating the flow of airunder pressure to the pres sure-responsive means, and sensing ;means including a flcxible element responsive in a first direction to the fiuid her to maintain subco-oling of the'fiuid at the condensing deviceoutlet, a second control member movable to actuate the power means to move the valve in said two directions, and means responsive to temperature to be affected closed position when the affected temperature exceeds a predetermined magnitude. 7

pressure within the condensing device and-responsive to the fluid temperature at'the outlet in a direction opposite to. said first direction, said sensing means also including biasing means'also eiiective in a direction'opposite to said first direction whereby said sensing means so COD: trols operation of the regulating means as. to maintain a sub-cooled condition ofthe. condensate at the outlet as determinedby said biasing means.

4. For use with a vapor condensing system of the kind.

having a vapor condensing device, an inlet conduit interconnecting the inlet of the condensing. device with a source of vapor-and an outlet conduit connected to a conmechanism .for regulating the suply ofnvapor to said condensing device comprising, a regulating valvedisposed m the conduit for governing the amount of vapor supplied .to the condensing; device, an electric motor con-- nected to the valve to move the valve in opening and clos- I having a movable pressure responsive element connected to the first variable potentiometer, temperature sensing means responsive to the fluid temperature at theoutlet of the vapor condensing device connected to the housing to movement of the valve, biasing means connected to the first potentiometer to bias the potentiometer in the. first;

direction, a conduit having anopen, end in communication with the interior of the condensing-device and con- .nected to the housing 'to -move the pressure responsive tinuously. open outlet of the condensing deviceycontrol I move the pressure responsive element and the first varia ble potentiometer in a first direction to cause closing 7. For use with a vapor condensing devicewherein vapor from a source thereof is condensed'and sub-cooled belowthe condensing temperature, a control-mechanism comprising a pneumatically operated valve for controlling the how of vaporto the condensingdevice, a thermostat valve for controlling the supply of air'under pressure to said pneumatically operatedvalve in response to I156 or decrease of the temperature to be, affected by the. con} operated valveso as to beefiective to maintain a sub cooled condition ofi-the condensate at the outlet as determined by said biasing means for any vapor pressure within the condensing device. E i

8. For use with: a vapor, condensing device wherein vapor from a source thereof is condensed and'sub-cooled belowthe condensingtemperature, a pneumatically operated valveforiciontrolling' the'flo wfofvaporto the condensing device,-cond uit means fonsupplying air under pressure to the pneumatically operated valve and having two parallel branches'leading from the, source of air under pressure, a firstjair pressure regulating valve incne of said branches and operative in response to rise or decrease of the temperature to be aifected by the condensing device for controlling the supply of air under pressure to said pneumatically operated valve to thereby regulate the supply of vapor to said condensing device in response to rise or decrease of the affected temperature, a second air pressure regulating valve in the second of said branches for regulating the flow of air under pressure to said pneumatieally operated valve, and sensing means for controlling the operation of said second air pressure regulating valve including means responsive to fluid temperature at the outlet of the condensing device for effecting movement of said second air pressure regulating valve in a first direction, said sen singalso including means responsive to fluid pressure in the condensing device for efiecting movement of said second air pressure regulating valve in a second direction, said sensing means further including biasing means for effecting movement of said second air pressure regulating valve in the same direction as the fluid temperature responsive means whereby the sensing means so controls the second air pressure regulating valve that the pneumatically operated valve so regulates flow of vapor to the condensing device that a sub-cooled condition of the condensate is maintained at the outlet of the condensing device,

References Cited by the Examiner UNITED STATES PATENTS 1,128,425 2/15 Dunham 236-58 1,304,100 5/19 Roesch 236-27 X 1,864,927 1/21 Fulton 23635.2 1,439,069 12/22 Cousins 236 1,455,633 5/23 Lundgaard.

1,806,393 5/31 Giesler 236- -4O 1,925,301 9/ 33 Campbell 251-28 1,952,683 3/34 Resek 236-99 1,962,676 6/34 Albright 236-82 X 2,029,203 1/ 36 Sodenberg 23 6-92 X 2,046,643 7/36 Mackintosh 23699 2,219,147 10/40 Binder 236-92 2,250,946 7/41 Brown 23 6-92 2,265,599 12/41 Grifi'ey 23692 2,266,202 12/ 41 Heinkel 236-91 2,389,244 1 1/ 45 Whaley.

EDWARD J. MICHAEL, Primary Examiner.

FREDERICK L. MATTESON, 111., FREDERICK KETTERER, PERCY L. PATRICK, Examiners. 

1. IN A VAPOR CONDENSING SYSTEM OF THE KIND WHEREIN A VAPOR CONDENSING DEVICE HAS AN INLET CONDUIT CONNECTED TO A SOURCE OF SUPPLY OF VAPOR AND A CONTINUOUSLY OPEN OUTLET CONNECTED TO AN OUTLET CONDUIT, A CONTROL MECHANISM FOR REGULATING THE SUPPLY OF VAPOR TO THE CONDENSATING DEVICE COMPRISING, A REGULATING VALVE DISPOSED IN THE CONDUIT FOR GOVERNING THE AMOUNT OF VAPOR SUPPLIED TO THE CONDENSING DEVICE, FIRST MEANS RESPONSIVE TO THE FLUID TEMPERATURE AT THE OUTLET OF THE CONDENSING DEVICE FOR MOVING THE VALVE IN A CLOSING DIRECTION, SECOND MEANS RESPONSIVE TO THE FLUID PRESSURE WITHIN THE CONDENSING DEVICE FOR MOVING THE VALVE IN AN OPENING DIRECTION, A FLEXIBLE ELEMENT CONNECTED TO THE VALVE TO EXERT A BIASING FORCE TO MOVE THE VALVE IN A CLOSING DIRECTION, AND CONDUIT MEANS CONNECTED TO SUPPLY A FLUID UNDER PRESSURE TO THE FLEXIBLE ELEMENT, WHEREBY THE PRESSURE ACTING ON THE FLEXIBLE ELEMENT MAINTAINS A DIFFERENTIAL BETWEEN THE TEMPERATURE OF THE FLUID AT THE CONDENSING DEVICE OUTLET AND THE SATURATION TEMPERATURE CORRESPONDING TO THE PRESSURE INTERNAL OF THE CONDENSING DEVICE SO AS TO MAINTAIN A SUB-COOLED CONDITION OF THE CONDENSATE AT THE OUTLET AS DETERMINED BY THE BIASING MEANS FOR ANY VAPOR PRESSURE WITHIN THE CONDENSING DEVICE. 